1. Field of the Invention
The present invention relates to well drilling and well drilling devices. More particularly, the present invention relates to a drill pipe float valve wherein the valve can be lowered into the hole in a preset partially open position and thereafter disengaged from the partially open preset position, and after such disengagement being freely movable allowing the valve to be opened (responsive to fluid circulation into the well) or closed (responsive to fluid back pressure acting upon the drill string bore).
2. General Background
It is known that during the lowering of drill pipe into a well having drilling fluid therein, it has been necessary to frequently stop and fill the pipe with fluid using a conventional float valve.
Examples of such earlier float valves are shown in U.S. Pat. Nos. 3,058,534 and 2,162,578. Such stopping and filling is undesirable from the standpoint of loss of valuable and expensive rig time.
Some float valves have been patented which have attempted to solve the problem of keeping the float valve partially open during filling. U.S. Pat. No. 3,446,237 to W. L. Haley issued May 27, 1969, provides a drill pipe float valve directed to the problem of maintaining the valve at an open position while lowering drill pipe into the well.
Other valve constructions are seen in U.S. Pat. Nos. 3,687,157 and 3,525,394.
U.S. Pat. Nos. 3,997,009, 2,481,397, 3,013,612 and 2,162,578 all show a valve having a sliding inner pipe that holds the valve open.
In U.S. Pat. Nos. 2,694,408 and 2,587,358 there is seen pressure actuated valves.